usb: xhci-mtk: add an optional xhci_ck clock

Some SoCs may have an optional clock xhci_ck (125M or 200M), it
usually uses the same PLL as sys_ck, so support it.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/1566542425-20082-2-git-send-email-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-mtk.c

@@ -216,6 +216,10 @@ static int xhci_mtk_clks_get(struct xhci_hcd_mtk *mtk)
 		return PTR_ERR(mtk->sys_clk);
 	}
 
+	mtk->xhci_clk = devm_clk_get_optional(dev, "xhci_ck");
+	if (IS_ERR(mtk->xhci_clk))
+		return PTR_ERR(mtk->xhci_clk);
+
 	mtk->ref_clk = devm_clk_get_optional(dev, "ref_ck");
 	if (IS_ERR(mtk->ref_clk))
 		return PTR_ERR(mtk->ref_clk);
@@ -244,6 +248,12 @@ static int xhci_mtk_clks_enable(struct xhci_hcd_mtk *mtk)
 		goto sys_clk_err;
 	}
 
+	ret = clk_prepare_enable(mtk->xhci_clk);
+	if (ret) {
+		dev_err(mtk->dev, "failed to enable xhci_clk\n");
+		goto xhci_clk_err;
+	}
+
 	ret = clk_prepare_enable(mtk->mcu_clk);
 	if (ret) {
 		dev_err(mtk->dev, "failed to enable mcu_clk\n");
@@ -261,6 +271,8 @@ static int xhci_mtk_clks_enable(struct xhci_hcd_mtk *mtk)
 dma_clk_err:
 	clk_disable_unprepare(mtk->mcu_clk);
 mcu_clk_err:
+	clk_disable_unprepare(mtk->xhci_clk);
+xhci_clk_err:
 	clk_disable_unprepare(mtk->sys_clk);
 sys_clk_err:
 	clk_disable_unprepare(mtk->ref_clk);
@@ -272,6 +284,7 @@ static void xhci_mtk_clks_disable(struct xhci_hcd_mtk *mtk)
 {
 	clk_disable_unprepare(mtk->dma_clk);
 	clk_disable_unprepare(mtk->mcu_clk);
+	clk_disable_unprepare(mtk->xhci_clk);
 	clk_disable_unprepare(mtk->sys_clk);
 	clk_disable_unprepare(mtk->ref_clk);
 }

drivers/usb/host/xhci-mtk.h

@@ -139,6 +139,7 @@ struct xhci_hcd_mtk {
 	struct regulator *vusb33;
 	struct regulator *vbus;
 	struct clk *sys_clk;	/* sys and mac clock */
+	struct clk *xhci_clk;
 	struct clk *ref_clk;
 	struct clk *mcu_clk;
 	struct clk *dma_clk;